______how to do it , we had to help him.

题目

______how to do it , we had to help him.
A.His not knowing B. The boy knowing not
C. He not knowing D. The boy's not having known
请详细分析

答案

______how to do it ,we had to help him.
A.His not knowing B.The boy knowing not
C.He not knowing D.The boy's not having known
选A
这是独立主格结构
因为前后两句主语不一致,所以用独立主格
【物主代词+非谓语】的结构
B应该是The boy’s not knowing
D不应该用完成时